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Lucene example source code file (WindowsDirectory.cpp)

This example Lucene source code file (WindowsDirectory.cpp) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

c, dword, getlasterror, getlasterror, java_org_apache_lucene_store_windowsdirectory_open, jnicall, jnicall, jnienv, jniexport, jniexport, lptstr, null, null, readfile

The Lucene WindowsDirectory.cpp source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
 
#include <jni.h>
#include "windows.h"

/**
 * Windows Native IO methods.
 */
extern "C" {

/**
 * Utility to format a Windows system error code into an exception.
 */
void throwIOException(JNIEnv *env, DWORD error) 
{
  jclass ioex;
  char *msg;
  
  ioex = env->FindClass("java/io/IOException");
  
  if (ioex != NULL) {
    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                  NULL, error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR) &msg, 0, NULL );
    env->ThrowNew(ioex, msg);
    LocalFree(msg);
  }
}

/**
 * Utility to throw Exceptions on bad input
 */
void throwException(JNIEnv *env, const char *clazz, const char *msg) 
{
  jclass exc = env->FindClass(clazz);
  
  if (exc != NULL) {
    env->ThrowNew(exc, msg);
  }
}

/**
 * Opens a handle to a file.
 *
 * Class:     org_apache_lucene_store_WindowsDirectory
 * Method:    open
 * Signature: (Ljava/lang/String;)J
 */
JNIEXPORT jlong JNICALL Java_org_apache_lucene_store_WindowsDirectory_open
  (JNIEnv *env, jclass ignored, jstring filename) 
{
  char *fname;
  HANDLE handle;
  
  if (filename == NULL) {
    throwException(env, "java/lang/NullPointerException", "filename cannot be null");
    return -1;
  }
  
  fname = (char *) env->GetStringUTFChars(filename, NULL);
  
  if (fname == NULL) {
    throwException(env, "java/lang/IllegalArgumentException", "invalid filename");
    return -1;
  }
  
  handle = CreateFile(fname, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, 
                      NULL, OPEN_EXISTING, FILE_FLAG_RANDOM_ACCESS, NULL);
  
  env->ReleaseStringUTFChars(filename, fname);
  
  if (handle == INVALID_HANDLE_VALUE) {
    throwIOException(env, GetLastError());
    return -1;
  }

  return (jlong) handle;
}

/** 
 * Reads data into the byte array, starting at offset, for length characters.
 * The read is positioned at pos.
 * 
 * Class:     org_apache_lucene_store_WindowsDirectory
 * Method:    read
 * Signature: (J[BIIJ)I
 */
JNIEXPORT jint JNICALL Java_org_apache_lucene_store_WindowsDirectory_read
  (JNIEnv *env, jclass ignored, jlong fd, jbyteArray bytes, jint offset, jint length, jlong pos)
{
  OVERLAPPED io = { 0 };
  DWORD numRead = -1;
  
  io.Offset = (DWORD) (pos & 0xFFFFFFFF);
  io.OffsetHigh = (DWORD) ((pos >> 0x20) & 0x7FFFFFFF);
  
  if (bytes == NULL) {
    throwException(env, "java/lang/NullPointerException", "bytes cannot be null");
    return -1;
  }
  
  if (length <= 4096) {  /* For small buffers, avoid GetByteArrayElements' copy */
    char buffer[length];
  	
    if (ReadFile((HANDLE) fd, &buffer, length, &numRead, &io)) {
      env->SetByteArrayRegion(bytes, offset, numRead, (const jbyte *) buffer);
    } else {
      throwIOException(env, GetLastError());
      numRead = -1;
    }
  	
  } else {
    jbyte *buffer = env->GetByteArrayElements (bytes, NULL);
  
    if (!ReadFile((HANDLE) fd, (void *)(buffer+offset), length, &numRead, &io)) {
      throwIOException(env, GetLastError());
      numRead = -1;
    }
  	
    env->ReleaseByteArrayElements(bytes, buffer, numRead == 0 || numRead == -1 ? JNI_ABORT : 0);
  }
  
  return numRead;
}

/**
 * Closes a handle to a file
 *
 * Class:     org_apache_lucene_store_WindowsDirectory
 * Method:    close
 * Signature: (J)V
 */
JNIEXPORT void JNICALL Java_org_apache_lucene_store_WindowsDirectory_close
  (JNIEnv *env, jclass ignored, jlong fd) 
{
  if (!CloseHandle((HANDLE) fd)) {
    throwIOException(env, GetLastError());
  }
}

/**
 * Returns the length in bytes of a file.
 *
 * Class:     org_apache_lucene_store_WindowsDirectory
 * Method:    length
 * Signature: (J)J
 */
JNIEXPORT jlong JNICALL Java_org_apache_lucene_store_WindowsDirectory_length
  (JNIEnv *env, jclass ignored, jlong fd)
{
  BY_HANDLE_FILE_INFORMATION info;
    	
  if (GetFileInformationByHandle((HANDLE) fd, (LPBY_HANDLE_FILE_INFORMATION) &info)) {
    return (jlong) (((DWORDLONG) info.nFileSizeHigh << 0x20) + info.nFileSizeLow);
  } else {
    throwIOException(env, GetLastError());
    return -1;
  }
}

} /* extern "C" */

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